Neural compensation mechanisms to regulate motor output during physical fatigue

Central fatigue refers to a progressive decline in the ability to activate muscles voluntarily. Although the neural mechanisms of central inhibition of the motor area during physical fatigue have been widely investigated, mechanisms supporting motor output during fatigue remain to be clarified. In this study, the compensation mechanisms to regulate physical fatigue were examined using a 160-channel whole-head-type magnetoencephalographic (MEG) system. The study group consisted of nine right-handed healthy participants. After enrollment, participants performed a fatigue-inducing physical task session in which they performed repetitive grips of the right hand at maximal voluntary contraction levels every second. Before and after the session, imagery of maximum grips of the right hand was performed for evaluation with MEG. Although beta-band event-related desynchronization (ERD) level of the motor movement-evoked magnetic field in the left sensorimotor area showed a trend toward reduction after the fatigue session, the ERD level of the motor movement-evoked magnetic field in the right sensorimotor area was increased after the session. The ERD level in the prefrontal area was increased after the fatigue-inducing session. The ERD level in the left sensorimotor area was positively associated with that in the right sensorimotor area after the fatigue-inducing task session. In addition, ERD levels in the left and right sensorimotor areas had trends toward positive correlations with that in the prefrontal area. These results suggest that the ipsilateral sensorimotor and prefrontal areas are brain regions associated with compensation mechanisms to support motor output under the condition of physical fatigue.